Spring @Value default value

By mkyong | Updated: August 27, 2023

Viewed: 7,438 (+130 pv/w)

Tags: spring spring3

This article shows how to provide a default value for the @Value annotation.

In the below code, if the property.name doesn’t exist in the application properties or environment, defaultValue will be assigned to the propertyName field.

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class SimpleComponent {

  @Value("${property.name:defaultValue}")
  private String propertyName;

  // getters, setters, etc
}

Table of contents:

• 1. Default value for @Value
• 2. Testing the default value for @Value
• 3. Download Source Code
• 4. References

P.S. Tested with Spring Boot 3.1.2

1. Default value for @Value

Review the project structure.

1.1 Spring default loads the application.properties from the classpath root, /src/java/resources.

  db.name=mkyong

1.2 In the below code, we use @Value to access the value defined with the db.name property key. If the db.name property key doesn’t exist in the application properties or environment, the hello (default value) will be assigned to the name field.

package com.mkyong;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class DatabaseService {

  @Value("${db.name:hello}")
  private String name;  // if db.name doesn't exist, we get hello

  public String getName() {
      return name;
  }

  public void setName(String name) {
      this.name = name;
  }
}

Starts the Spring Boot application.

package com.mkyong;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;

@org.springframework.boot.autoconfigure.SpringBootApplication
public class SpringBootApplication implements CommandLineRunner {

  @Autowired
  private DatabaseService dbConfig;

  @Override
  public void run(String... args) throws Exception {
      System.out.println(dbConfig.getName());
  }

  public static void main(String[] args) {
      SpringApplication.run(SpringBootApplication.class, args);
  }
}

Output

  mkyong

1.3 Now, we comment out the property key db.name in the application.properties.

# comment out to test the default value
# db.name=mkyong

Rerun the application, and we get the output hello.

  hello

2. Testing the default value for @Value

2.1 We create a new test.properties with empty content for testing.

# comment to test the default value
# db.name=mkyong

2.2 We can use @TestPropertySource to load values from the test.properties file.

package com.mkyong;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.test.context.TestPropertySource;
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;

import static org.junit.jupiter.api.Assertions.assertEquals;

// easy but load entire context, no good.
// @SpringBootTest

// Keep test in minimal configuration
@SpringJUnitConfig
@TestPropertySource("classpath:test.properties")
public class ApplicationTest {

  @Autowired
  private DatabaseService dbServer;

  @Test
  public void testDefaultDatabaseName() {
      assertEquals("hello", dbServer.getName());
  }

  // Mock Configuration within the test class
  @Configuration
  static class TestConfig {
      @Bean
      public DatabaseService dbServer() {
          return new DatabaseService();
      }
  }

}

3. Download Source Code

4. References

• SpringDoc – PropertySource
• Spring Boot – Externalized Configuration
• Spring @PropertySource example
• Testing JSON in Spring Boot
• Spring Boot @ConfigurationProperties example
• Access values from application.properties in Spring Boot